where we have assumed the simple case where the DM is the Majorana fermion \(\chi =\chi _L + (\chi _L)^C\)  and neglect the mixing with the other fermions present in the theory for simplicity. The factor 3/4 is the baryon number of the dark matter divided by 2, the latter comes from the 1/2 factor in the projector. The gauge boson has vector coupling to quarks since \(Z_B\)  is associated to baryon number.
In this paper we will focus on this scenario since it is realized in both models in Refs. [1]}, [2]}. In the above equation, \(\theta _B\)  is the mixing angle between the SM Higgs and the new Higgs present in the theory to break the local baryon number symmetry, \(S_B\sim (1,1,0,3)\) . In the above equation \(h_1\)  and \(h_2\)  are the physical states present in the theory.
